Bovine endometrial epithelial cells are able to internalize Escherichia coli in vitro.

The uterus of postpartum cows usually becomes contaminated with bacteria. To eliminate these bacterial contaminants, during uterine involution, the endometrium initiates an innate immune response carried out by professional immune cells but also by endometrial epithelial cells (EpC) and stromal cells (StC). A better understanding of the interactions between endometrial cells and bacteria such as Escherichia coli may contribute to improving diagnostic and therapeutic strategies for uterine diseases, and thus to enhancing conception efficiency in dairy cattle. This study aimed to investigate the capacity of bovine endometrial EpC and StC to adhere to and internalize E. coli in vitro. A primary culture of bovine endometrial cells was performed and challenged with FITC-labeled E. coli. Flow cytometry demonstrated that, unlike StC (P = 0.883), EpC significantly internalized E. coli (P = 0.013). This finding was further confirmed by confocal immunofluorescence imaging. Given that E. coli is typically considered an extracellular bacterium, these findings provide the first evidence showing that bovine endometrial EpC can adhere and internalize E. coli.